Endoscopic endonasal extradural posterior clinoidectomy: A key maneuver to access the retrosellar and upper retroclival area.

BACKGROUND: Endoscopic endonasal posterior clinoidectomy represents an important maneuver to improve access and visualization of the retrosellar and upper clivus area [1]. Three different techniques have been described in order to access and remove the posterior clinoid: 1) the intradural pituitary transposition [2], the interdural pituitary transposition [3] and a completely extradural technique [4]. CASE DESCRIPTION: We present here a case of retrosellar and retroclival chordoma that has been removed through endoscopic endonasal approach. Technical nuances of the endonasal extradural posterior clinoidectomy are presented. CONCLUSION: Endoscopic endonasal extradural posterior clinoidectomy allows to access this complex anatomical region with the advantage of avoiding major bleeding from the cavernous sinus and endocrinological impairment.

Posterior Fossa Craniopharyngioma Arising from the Inferior Medullary Velum.

We report the case of a 63-year-old man with a midline posterior fossa tumor and peculiar imaging features where we were unsure of the nature of the lesion preoperatively. Histopathology revealed it to be a craniopharyngioma. It appeared to arise from the inferior medullary velum, a site not described before in the literature. The previous four cases mentioned in literature and speculations on the origins in this uncommon site are discussed.

When is the radiology report of posterior fossa containing cyst/cystic-like CSF collection of clinical or surgical significance?

OBJECTIVE: The nomenclature characterizing posterior fossa (PF) extraventricular (EV) CSF collections in radiological reports can be quite variable, leading to uncertainty about the subsequent clinical course that may result in multiple follow-up imaging studies that may not be needed and occasionally to operative intervention that is not warranted. The important factor is the mass effect of the PF EV CSF collection on adjacent structures, the presence of hydrocephalus, and the likelihood of the CSF collection increasing in size over time. METHODS: The authors respectively reviewed the imaging database at Children's Hospital Los Angeles to identify all radiological reports from 2000 to 2015 indicating the presence of an EV CSF collection in the PF that was characterized as containing an arachnoid cyst, being cystic, or being an abnormal CSF collection. RESULTS: Of the 332 reports in 65 patients, the PF EV CSF collection was described as an arachnoid cyst or cystic in 306 with 20 different terms being used. In those patients who underwent multiple imaging studies, the PF EV CSF collection was often described differently in each report. Of this group, 47 (72%) patients did not undergo PF surgery. Eighteen (28%) patients did undergo PF surgery, of whom 14 had both hydrocephalus and brainstem displacement, 2 had brainstem displacement but no hydrocephalus, and 2 had neither brainstem displacement nor hydrocephalus and in retrospect did not benefit from PF surgery. CONCLUSIONS: The terminology in radiology reports describing EV PF CSF collections is variable, is inconsistent, and does not correlate well with clinical management or the need for PF surgery. Significant brainstem displacement and hydrocephalus in the presence of EV PF CSF collection is highly correlated with the need for PF surgery. The incidence of a PF EV CSF collection increasing to become symptomatic becomes more remote the older the patient is at the time of diagnosis as compared with those that occur mainly in infancy. There are true EV CSF cysts in the PF, but the ones that are of consequence are those that exert pressure on the brainstem, obstruct CSF flow, or both. Calling any increased amount of CSF in the PF a "cyst" or "cystic" can cause uncertainty, leading to one or more subsequent imaging studies or, in rare cases, unwarranted operative intervention.

Comparative Analysis of Patients Undergoing Microvascular Decompression for Trigeminal Neuralgia Caused by Solely Arterial or Solely Venous Compression.

OBJECTIVE: Trigeminal neuralgia (TN) due to venous compression is far less common than that due to arterial compression, and its pathogenesis is less clear. We investigated the clinical and imaging features of TN caused by solely venous compression by measuring the morphologies of the posterior cranial fossa (PCF) and the trigeminal nerve. METHODS: We retrospectively reviewed records of TN patients who underwent microvascular decompression at our institution and extracted cases with solely arterial or solely venous compression. Preoperative magnetic resonance imaging was used to find the length (Y), width (X), height (Z), and volume (V) of the PCF, the angle between the trigeminal nerve and pons, and the distance between Meckel's cave and the root entry zone of the trigeminal nerve. RESULTS: Of 152 patients, 24 had TN caused solely by venous compression. The value of Y was significantly smaller in the venous group than the arterial group (P < 0.01). The trigeminal nerve and pons was significantly smaller in the venous group (P < 0.01). We hypothesized that TN patients with solely venous compression had a characteristic PCF morphology with a short anteroposterior diameter (Y), such that age-related changes in brain morphology could alter the course of the trigeminal nerve and cause compression by a vein. CONCLUSIONS: The morphological features of the PCF differed between patients with TN of venous and those with TN of arterial etiology. Age-related changes in brain morphology and changes of course of the trigeminal nerve may also add to the possibility of developing TN, especially of venous etiology.

Clinical, Anatomical, and Histological Features of the Rhomboid Lip and Considerations for Surgery Using a Retrosigmoid Approach: A Retrospective Study.

OBJECTIVE: The rhomboid lip is a neural tissue encountered during cerebellopontine angle surgery, with differing shape and extent among individuals. This study aimed to investigate the variation of rhomboid lips during posterior fossa surgery. METHODS: In this retrospective study, we examined posterior cranial fossa surgeries performed using a retrosigmoid approach. Rhomboid lips were classified according to thickness, extent, and appearance, with some subjected to histological analysis. T2-weighted magnetic resonance imaging of rhomboid lips was conducted. RESULTS: Among 304 surgeries, rhomboid lips were observed in 75 patients who underwent schwannoma or meningioma resection, facial spasm-related neurovascular decompression, and other surgeries (37, 2, 32, and 4 patients, respectively). Rhomboid lips were categorized based on apparent thickness: thin membranous type, resembling an arachnoid membrane, and thick parenchymal type. Rhomboid lip extension was classified by position relative to the choroid plexus: nonextension, lateral extension, and jugular foramen (41, 22, and 12 patients, respectively). Veins were observed on the rhomboid lip surface in 37 cases. The rhomboid lip was visible in only 1 case (parenchymal jugular foramen type) on magnetic resonance imaging. Histologically, the rhomboid lip comprised an ependymal cell layer, a glial layer, and connecting tissue. The glial layer thickness determined the rhomboid lip thickness, which was greater in the parenchymal type than in the membrane type. In 42 patients, the rhomboid lip was dissected with no complications observed. CONCLUSIONS: Morphological classification of the rhomboid lip and understanding of its anatomical details contribute to safe surgical field development for neurosurgeons.

Perioperative Segmentation of the Posterior Fossa and the Keel of Goodrich in Surgical Outcomes of Chiari Malformations.

BACKGROUND: Chiari I malformation (CM-I) is defined as the extension of brain tissue into the spinal cord. This study aimed to refine the methodology for the acquisition of 3-dimensional measurements of the posterior fossa and introduce occipital keel size as a new marker and its impact in patients with CM. METHODS: In this retrospective study, all patients who underwent Chiari decompression surgery at Montefiore Medical Center from April 2012 to April 2022 were included. Perioperative clinical information was obtained in addition to maximal keel thickness (KT), foramen magnum area, and preoperative and postoperative posterior fossa volumes for each patient and age-matched controls. Volumetric measurements were obtained using artificial intelligence-based semiautomated segmentation. RESULTS: A total of 107 patients with CM including 37 males, and 70 females were studied with a mean age of 26.56 ± 17.31 compared with 103 controls without CM. The comparison between the CM and the general population groups demonstrated a significantly increased keel size in Chiari patients. Keel size had a significant relationship with dysphagia, paresthesia, and intraoperative blood loss, while posterior volume change had a significant relationship with sex and early symptomatic improvement. The Foramen magnum area was related to tonsillar descent and more prominent in patients with spina bifida. CONCLUSIONS: The Keel of Goodrich is a new anatomical factor that should be taken into consideration when evaluating preoperative symptoms, and intraoperative complications in patients with CM-I. Volumetric analyses demonstrated that posterior fossa volume change had a significant impact on early symptom improvement in patients with Chiari, as did the choice of operative approach. The routine use of semiautomated segmentation of the posterior fossa may help stratify Chiari patients in the future and should be implemented in routine clinical care.

Posterior Cranial Fossa Surgery with a 3 Dimensional Exoscope: A Single-Center Survey-Based Analysis and a Literature Review.

OBJECTIVE: The potential advantages of exoscopy have been discussed theoretically for a long time. Such a concept holds significance, especially in the specific setting of the posterior cranial fossa (PCF), characterized by complex anatomy and long and narrow surgical corridors with relatively extreme working angles. We aimed to: 1) analyze the institutional preliminary case-based data on the use of the Robotic 3D Exoscope AEOS Aesculap in three different PCF approaches: retrosigmoid (RSA), midline suboccipital (MSA), and supracerebellar infratentorial via feedbacks was collected using a 20-point questionnaire, and 2) perform a comprehensive review of the literature concerning the use of EX in PCF surgery. RESULTS: A total of 38 patients with neurosurgical pathologies underwent a neurosurgical procedure using the EX (Robotic 3D exoscope AEOS Aesculap) at our institution between January and March 2022. 21 surgeons were involved in the abovementioned PCF surgeries and answered the questionnaire. The main perceived advantages were in terms of ergonomics (67%), magnification (52%), and visualization of extreme angles. The main reported disadvantage was color vision (16, 76%), followed by manual mobility (24%). Concerning the review, the search of the literature yielded a total of 177 results. Upon full-text review, 17 articles were included, including 153 patients. CONCLUSIONS: In conclusion, our study provides a comprehensive evaluation of the advantages and challenges associated with using the exoscope in posterior fossa surgery, setting a precedent as the first to report on a questionnaire-based analysis of exoscope utilization in this specific domain.

Pineal Tumor Surgery-The Choice of the Approach Related to Tumor Characteristics and Posterior Fossa Anatomy.

OBJECTIVE: This research aimed to determine whether an adequate surgical approach can be chosen based on clearly defined values of anatomical landmarks (tentorial angle) and tumor size and extension. METHODS: We conducted a retrospective analysis of patients operated on because of pineal tumors. The cohort was divided depending on the surgical approach. On preoperative magnetic resonance imaging, we measured maximal diameters, tumor volume, and tumor propagation. In the group of patients operated with the supracerebellar infratentorial approach, we also tested the correlation of tentorial angle with residual tumor. Differences among groups in resection, complications rate, and outcome were tested by the χ2 test. Finally, in both groups, the correlation of residual tumor with tumor volume, propagation, and diameters was tested using the receiver operating characteristic curve. RESULTS: In the group operated with a supracerebellar approach, total resection was achieved in 78% of the patients. The critical value of cranio-caudal diameter correlated with tumor residue was 31 mm, for lateral-lateral diameter 25 mm, for the lateral extension 14 mm, and tumor volume 12 cm3. Tentorial angle did not influence the extent of the resection. In the group operated with an occipital transtentorial approach, the critical tumor volume related to tumor residue was 9 mm3, anterior-posterior diameter 29 mm, and cranio-caudal diameter 28 mm. The extent of the resection was significantly higher in the supracerebellar group. CONCLUSIONS: In both approaches, tumors larger than 3 cm show an increased risk of subtotal resection. Except when most tumor volume is localized above the venous system, we advocate a supracerebellar corridor as an effective approach that is not limited by tentorial angle.

A watch, wait, and rescan approach for incidental benign-appearing notochordal lesions of the skull base.

OBJECTIVE: The aim of this study was to describe the natural history of incidental benign-appearing notochordal lesions of the skull base with specific attention to features that can make differentiation from low-grade chordoma more difficult, namely contrast uptake and bone erosion. METHODS: In this retrospective case series, the authors describe the clinical outcomes of 58 patients with incidental benign-appearing notochordal lesions of the clivus, including those with minor radiological features of bone erosion or contrast uptake. RESULTS: All lesions remained stable during a median follow-up of almost 3 years. Thirty-seven (64%) patients underwent contrast-enhanced MRI; lesions in 14 (38%) of these patients exhibited minimal contrast enhancement. Twenty-seven (47%) patients underwent CT; lesions in 6 (22%) of these patients exhibited minimal bone erosion. CONCLUSIONS: These data make the case for monitoring selected cases of benign-appearing notochordal lesions of the clivus in the first instance even when there is minor contrast uptake or minimal bone erosion.

PHACES syndrome and multi-regional odontodysplasia: a case report.

PHACES syndrome is an acronym for the syndromic presentation of Posterior fossa malformation, Hemangioma, Arterial anomalies, Coarctation of aorta/cardiac defects, Eye abnormalities and Sternal malformations. Infantile hemangiomas are the most common tumors of infancy. Regional odontodysplasia, commonly referred to as "ghost teeth", is a rare localized developmental malformation of enamel and dentin with varying levels of severity that results in unusual clinical and radiographic appearances of affected teeth. This report describes a rare case of a two-year-old Caucasian male diagnosed with PHACES syndrome also presenting with multi-regional odontodysplasia. Ten of twenty teeth were dysplastic. The patient was treated under general anesthesia in a hospital setting. All affected primary teeth were extracted due to sensitivity, abscess and extremely poor long-term prognosis. Moving forward, a long-term interdisciplinary approach will be necessary to address this child's dentition as it develops.

Predicting the Need for Occipitocervical Fusion for Patients with Lower Clival Chordoma: A Single-Center Retrospective Study.

OBJECTIVE: To assess the impact of tumor extension into the occipital condyle (OC) in lower clival chordoma management and the need for occipito-cervical fusion (OCF). METHODS: A retrospective analysis was conducted on 35 patients with lower clival chordoma. The preoperative area of the intact OCs, Hounsfield units, and the integrity of the apical ligament and the tectorial membrane were assessed using preoperative imaging. RESULTS: Seven (20%) patients were in the OCF group. The OCF group exhibited a higher prevalence of preoperative pain in the neck or head (P = 0.006), ligament absence (P = 0.022), and increased propensity for postoperative wound issues (P = 0.022) than the non-OCF group. The OCF group had less intact OCs (P < 0.001) and higher spinal instability neoplastic score (P = 0.002) than the non-OCF group. All patients with intact OCs < 60% underwent OCF, and those with OCs ≥ 70% were treated without OCF. Those with OCs between 60% and 69% underwent OCF if the ligaments were eroded, and did not undergo OCF if the ligaments were intact. Treatment strategies varied, with endoscopic endonasal approach alone being common. Radiation therapy was administered to 89% of patients. All 3 patients treated with OCF after tumor resection had wound issues; none treated with OCF before resection had wound issues. None developed atlanto-occipital instability. Survival rates did not significantly differ between groups. CONCLUSIONS: In the absence of mobility-related neck pain, patients with lower clival chordoma and intact OC ≥ 60%, intact apical ligament, and intact tectorial membrane, may not require OCF.

Institutional Experience of Post-Traumatic Posterior Fossa Extra Dural Hematoma: A Prospective Longitudinal Study.

AIM: To analyze clinical and imaging characteristics of post-traumatic posterior fossa extradural hematoma (PFEDH). MATERIAL AND METHODS: Between 2018 and 2022, 51 patients were admitted to our tertiary care trauma center with a diagnosis of PFEDH. The management decision was tailored by an individual consultant based on clinicoradiological findings. We did a prospective analysis of patient characteristics, radiology, clinical presentation, management, and outcome at discharge and onemonth follow-up. RESULTS: Of the 51 patients diagnosed with a PFEDH, 45 (88.2%) were male, and six (11.8%) were female with a mean age of 31.2 years (range 2-77 years). Twenty-six patients needed surgical evacuation of the EDH, while the rest 25 patients were managed conservatively. There was one crossover patient from the conservative to the surgical arm. Road traffic accidents (RTA) were the most common cause of injury (n=35; 68.6%), followed by falls from height (n=16; 31.4%). Most patients presented with vomiting and loss of consciousness (LOC). At presentation, 30 patients (58.5%) had a GCS 15. Seven patients (13.7%) presented with a GCS of 9-14, and 14 patients (27.5%) with GCS ≤ 8. The mean EDH volume in conservatively and surgically managed patients was 14.1 and 25.1cc, respectively. Five patients (9.8%) had significant midline shift with obliteration of basal cisterns, 15 patients (29.4%) had effacement of the fourth ventricle, and 11 patients (21.5%) had the presence of hydrocephalus. All patients with features suggestive of tight posterior fossa (hydrocephalus, obliterated basal cisterns, and fourth ventricle compression) needed surgical intervention. Of the 25 conservatively managed patients, 24 (96%) had favorable GOS scores at discharge, while one (4%) had an unfavorable score. 16/26 (61.5%) surgically treated patients had a good outcome at discharge (GOS=4-5), while ten patients (38.4%) had adverse outcomes (GOS < 4). Initial EDH volume was inversely correlated with presenting GCS and GOS with a mean volume of 21.5 ± 8.5 cc in patients presenting with a GCS ?8. Patients with a GCS of 15 at presentation had a mean EDH volume of 16.1 ± 8.2 cc. Patients with smaller EDH had much higher GOS scores than patients with higher volume EDH (GOS 1 = 22.0 ± 9.83 cc vs. GOS 5 = 18.9 ± 12.2 cc). Outcomes mainly depended on factors like GCS at arrival and associated supratentorial, thoracic/ abdominal polytrauma. CONCLUSION: In patients with a clot volume of < 15 cm3 and GCS of 15 at presentation with no mass effect and absence of tight posterior fossa, a conservative trial under strict clinicoradiological monitoring in a neuro-critical multidisciplinary setting can be offered with good results. In cases of altered GCS, findings of a TPF, or clinicoradiological deterioration, immediate surgery is warranted.

The Displacement Patterns of Petrous Internal Carotid Artery and Its Morphometric Relations with Vidian Canal in Petroclival Chondrosarcomas Relevant to Extended Endoscopic Endonasal Approaches: A Radiological Study.

BACKGROUND: Extended endoscopic endonasal approaches (EEAs) to petroclival chondrosarcomas (PCs) require a thorough understanding of skullbase anatomy, especially the anatomy of petrous internal carotid artery (pICA), as ICA injury is the most dreaded complication of extended EEAs. We conducted this study to determine the displacement patterns of pICA in patients with PCs. METHODS: Contrast enhanced computed tomography scan and angiography images of patients with PCs were analyzed for following parameters-antero-posterior, cranio-caudal, medio-lateral, and direct distances between anterior genu of petrous internal carotid artery (AGpICA) and posterior end of Vidian canal (pVC). pICA encasement/narrowing by tumor was noted on magnetic resonance imaging. RESULTS: We studied 11 patients with histopathologically proven PCs. pICA encasement/narrowing and pVC destruction were observed in one patient each. The mean antero-posterior and cranio-caudal distances on tumor side/normal side were 7.7 ± 1.9/6.4 ± 1.0 mm & 4.5 ± 1.5/3.4 ± 0.9 mm, respectively. The overall displacement was posterior & superior. Medio-lateral displacement was seen in 4 patients (lateral in 3 and medial in 1). In rest, AGpICA was centered on pVC. The mean direct distance was 9.4 ± 2.5 mm. In 3 patients with displacement seen in all three axes, direct distance was measured by the "cuboid method." Overall, posterior-superior-lateral, posterior-superior, and anterior-inferior were the common displacement patterns of AGpICA relative to pVC. CONCLUSIONS: The displacement patterns of AGpICA in PCs are variable. An individualized approach with meticulous analysis of preoperative imaging can help in determining the relation between AGpICA and pVC. This detailed morphometric information can facilitate better orientation to altered anatomy, which can be helpful in preventing pICA injury during extended EEAs.

[Endoscopic transnasal resection of clival meningiomas]. / Rezul'taty endoskopicheskogo transnazal'nogo udaleniya meningiom oblasti skata.

BACKGROUND: Surgical treatment of ventral and ventrolateral meningiomas of posterior cranial fossa is difficult in modern neurosurgery. This is due to peculiarities of approach to these areas and concentration of critical structures (cranial nerves and great vessels). Currently, endoscopic transnasal approach to these meningiomas allows partial, and in some cases, total resection. However, this technique is not widespread. OBJECTIVE: To analyze the world literature data on postoperative outcomes in patients with clival and petroclival meningiomas after endoscopic transnasal resection. MATERIAL AND METHODS: We analyzed 22 articles representing treatment of 61 patients with clival and petroclival meningiomas. RESULTS: Total or near-total resection was achieved in 22.9% of cases, subtotal resection - 40.9%, partial resection - 26.2% (data were not provided in other cases). Even partial and subtotal resection leads to significant regression of symptoms. CONCLUSION: Endoscopic transnasal surgery is a full-fledged alternative to transcranial approaches in surgical treatment of clival meningiomas. It is also an additional option for patients with petroclival meningiomas after ineffective transcranial approaches. Transnasal tumor shrinkage and devascularization lead to brainstem decompression, regression of hydrocephalus and baseline clinical symptoms.

Endoscope-Assisted Microsurgery for Posterior Fossa Skull Base Meningioma Surgery: Technique and Results.

BACKGROUND AND OBJECTIVES: Surgery of posterior fossa meningiomas is extremely challenging even for experienced skull base surgeons because of the close proximity to cranial nerves and tight spaces. Endoscope-assisted surgery for posterior fossa meningiomas can enable a high degree of tumor resection even when using small approaches. This study describes the advantage of endoscope-assisted microneurosurgery in resection of posterior fossa skull base meningiomas and the clinical outcome. METHODS: All endoscope-assisted surgeries for resection of posterior fossa meningiomas performed between 2002 and 2016 in our department were retrospectively analyzed. For data acquisition, the patient files were used. Tumor size and extent of resection were evaluated on pre- and postoperative magnetic resonance imaging. The value of endoscope assistance was assessed according to the intraoperative videos and the surgical notes. Complications and long-term outcomes were evaluated. RESULTS: We identified 39 female and 10 male patients. The mean age of the patients at the time of surgery was 55 years, ranging from 25 to 78 years. The mean follow-up was 93.8 months. A total of 41% of the tumors were large to giant. The retrosigmoid approach was used in most patients (45). A gross total resection could be achieved in 38 patients (78%). In 11 patients (22%), a near total resection was performed. In 27 patients (55%), a hidden residual tumor, which could not been visualized with the operating microscope, was identified with the endoscope. In 6 patients (22.2%), the internal auditory canal was visualized, in 9 patients (33.3%), the Meckel's cave was visualized, and in 5 patients (18.5%), both were visualized under endoscope assistance. In 26 of those patients (96.3%), the residual tumor was resected under endoscopic view. CONCLUSION: Endoscope-assisted surgery for posterior fossa skull base meningiomas enables a high degree of tumor resection, avoids more invasive skull base approaches, and reduces the amount of cerebellar retraction.

'Choroid bar': easy-to-seek marker of normal posterior fossa at 12-14 weeks' gestation.

OBJECTIVES: Our objectives were: (1) to assess the visualization rate of the choroid bar in a consecutive series of 306 first-trimester scans; (2) to verify, in this cohort of fetuses, the normality of the posterior fossa later in pregnancy; and (3) to confirm the non-visualization of the choroid bar in a retrospective series of fetuses with posterior fossa malformations. METHODS: This study included a prospective and a retrospective series. The former comprised 306 fetuses undergoing routine obstetric ultrasound at our unit in both the first and second trimesters over a 6-month period, while the latter comprised 12 cases of posterior fossa malformations. In the prospective study, the presence of the choroid bar, which is defined as a visually continuous, homogeneously hyperechogenic, thick structure bridging the cisterna magna from side to side, was evaluated at the end of the first-trimester nuchal translucency scan. In the retrospective study, previously acquired three-dimensional volume datasets were processed in order to assess whether the choroid bar could be visualized in cases of open spinal dysraphisms and vermian cystic anomalies. In the prospective study, confirmation of a normal posterior fossa was based on the sonographic features of this anatomical region at the time of the second-trimester anomaly scan at 19-21 weeks' gestation, while, in the retrospective study, it was based on autopsy results, when available, or further direct imaging of the defect later in pregnancy. RESULTS: In the prospective study, the choroid bar could be visualized in all 306 fetuses, on transabdominal ultrasound in 287 (93.8%) cases and on transvaginal ultrasound in 19 (6.2%) cases. The choroid bar was displayed with a ventral/dorsal approach in 67 (21.9%) cases, with a lateral approach in 56 (18.3%) cases and with both in 183 (59.8%) cases. All 306 cases were confirmed to have a sonographically normal posterior fossa at 19-21 weeks. On the other hand, in the retrospective study, it was not possible to visualize the choroid bar in any of the fetuses with posterior fossa malformations. CONCLUSIONS: We have described a new sign, the choroid bar, consistent with a normal posterior fossa at 12-14 weeks' gestation. The choroid bar provides the option of screening for major abnormalities of the posterior fossa, since its absence raises suspicion of both open spinal dysraphisms and posterior fossa cystic malformations. At the same time, it is easy to visualize, as it can be seen with all lines of insonation. © 2023 International Society of Ultrasound in Obstetrics and Gynecology.

Full-Endoscopic Technique for Posterior Fossa Decompression in Chiari Malformation.

BACKGROUND AND IMPORTANCE: Full-endoscopic techniques are well-described for spinal procedures. Although endoscopic-assisted techniques are reported for posterior fossa decompression (PFD) in Chiari malformation (CM), a full-endoscopic technique is yet to be reported in these patients. The aim of this study was to present and describe a full-endoscopic technique for PFD in patients with CM. CLINICAL PRESENTATION: Two patients diagnosed with CM were operated on by the full-endoscopic PFD technique. The patients consented to the procedure and to the publication of their image. An endoscope with an oval shaft cross-section with a diameter of 9.3 mm, a working length of 177 mm, a viewing angle of 20°, and a working channel of 5.6 diameters were used. Operative videos were recorded. The surgical steps were easily applied after the clear anatomic landmarks, such as the C1 posterior tubercle and the rectus capitis posterior minor muscles. The patients were followed up for 6 months. Both patients were symptom-free with a significant decrease in Visual Analog Scale score and a good functional outcome assessed by Chicago Chiari Outcome Scale after surgery without any complications. CONCLUSION: All the steps of the full-endoscopic technique for PFD described by the authors in their previous human cadaveric study were also feasible on patients with CM.

The Effect of Posterior Fossa Decompression Surgery on Brainstem and Cervical Spinal Cord Dimensions in Adults with Chiari Malformation Type 1.

OBJECTIVE: Posterior fossa decompression (PFD) surgery creates more space at the skull base, reduces the resistance to the cerebrospinal fluid motion, and alters craniocervical biomechanics. In this paper, we retrospectively examined the changes in neural tissue dimensions following PFD surgery on Chiari malformation type 1 adults. METHODS: Measurements were performed on T2-weighted brain magnetic resonance images acquired before and 4 months after surgery. Measurements were conducted for neural tissue volume and spinal cord/brainstem width at 4 different locations; 2 width measurements were made on the brainstem and 2 on the spinal cord in the midsagittal plane. Cerebellar tonsillar position (CTP) was also measured before and after surgery. RESULTS: Twenty-five adult patients, with a mean age of 38.9 ± 8.8 years, were included in the study. The cervical cord volume increased by an average of 2.3 ± 3.3% (P = 0.002). The width at the pontomedullary junction increased by 2.2 ± 3.5% (P < 0.01), while the width 10 mm caudal to this junction increased by 4.2 ± 3.9% (P < 0.0001). The spinal cord width at the base of second cervical vertebra and third cervical vertebra did not significantly change after surgery. The CTP decreased by 60 ± 37% (P < 0.0001) after surgery, but no correlation was found between CTP change and dimension change. CONCLUSIONS: The brainstem width and cervical cord volume showed a modest increase after PFD surgery, although standard deviations were large. A reduction in compression after PFD surgery may allow for an increase in neural tissue dimension. However, clinical relevance is unclear and should be assessed in future studies with high-resolution imaging.

Combined and staged retrosigmoid, extended middle fossa, and endoscopic transnasal approach to a petroclival chondrosarcoma: how I do it.

BACKGROUND: Tumors of the petroclival region with multicompartment extension can be difficult to address with a single surgical approach. METHOD: We present the case of a patient with a large chondrosarcoma centered at the right petroclival fissure with extension into the cavernous sinus, the region beneath the cavernous sinus, cerebellopontine angle with deformation of the pons, and prevertebral space. A staged complete resection was performed using a stage 1 single-incision combined right retrosigmoid craniotomy and extended middle fossa craniotomy, followed by a stage 2 endoscopic transnasal approach. CONCLUSION: A combined approach to selected petroclival tumors can maximize safe resection.

Combined retrosigmoid and middle fossa approach for a small, superiorly located petroclival meningioma: how I do it.

BACKGROUND: Petroclival meningiomas pose significant surgical challenges because of their deep location and complex surrounding neurovasculature. The use of multiple surgical approaches can optimize safe tumor removal from multiple anatomic compartments. METHOD: We describe a patient with a growing superior petroclival meningioma centered at the posterior clinoid with extension into Meckel's cave that was successfully removed with a combined retrosigmoid and subtemporal middle fossa approach. This strategy avoided the need for anterior petrous bone drilling and tentorial splitting. CONCLUSION: A combined retrosigmoid and subtemporal middle fossa approach can provide safe access to tumors spanning the supra- and infratentorial compartments.